The present invention relates generally to the field of earthwork and lawn aerator or perforator apparatus. More specifically, the present invention relates to an abrading tine for use with turf aeration apparatus that decreases the compaction of soil caused by conventional smooth tines and results in improved root mass and water infiltration.
Soil compaction is the foremost turf problem, particularly for golf courses and athletic fields or other lawn areas subject to heavy traffic. Soil compaction occurs when soil particles are pressed together and pore spaces, or spaces between soil particles, are reduced. This reduction in pore space is detrimental as it impedes root growth, prevents oxygen from reaching the roots and, because water must flow through these pore spaces, a lack of these spaces means less water is available to the roots. Soil compaction also prevents root hair development and clipping yield is reduced. However, soil compaction does not directly deteriorate turf. Instead, it affects other factors such as soil aeration, soil strength, plant and soil moisture relationships, and soil temperatures. These factors, in turn, affect how turf grass grows.
Foot and vehicular traffic are the major causes of soil compaction. These types of compaction are most prevalent on high trafficked areas such as golf course greens where all golfers must converge in order to complete their respective holes. After a while, this compaction continues to build up and turf quality and vigor become seriously impaired.
The most widely used form of controlling soil compaction is cultivation. While it would not be practical to tear up the turf every time compaction problems arise, a selective tillage method called coring has been used as a satisfactory method of getting rid of compaction with minimal disturbance to the turf. Coring is achieved by taking a metal tube, called a tine or spoon, mounted on a crank shaft and vertically inserting it into the ground. The tines remove a small core of soil usually measuring about 10 cm in length and about 1 cm in diameter. Once the cores are removed, a topdressing usually consisting of sand is added in place of the cores. The topdressing improves infiltration, increases pore space, encourages root growth, and aids in the decomposition of thatch. Coring alone is also effective in releasing harmful gases that can build up in the soil. It improves wetting of dry soils, causes quicker drying of persistently wet soils, increases root development and shoot growth around the hole, and encourages turf grass response to fertilizers. If practiced regularly, core cultivation can be effective in alleviating many problems that affect turf grass growth.
Numerous types of turf aeration apparatus have been developed to accomplish the process of core cultivation. Examples of vertically powered devices can be found in U.S. Pat. Nos. 2,068,828, 2,638,831, 2,800,066, 3,834,464, 4,081,304, 4,602,687, 4,658,909, 4,750,565, 4,884,637 and 5,207,278. Most of these vertically powered turf aeration apparatus utilize a sharpened slightly tapered hollow metal tube as the tine that is vertically inserted and withdrawn from grass turf so as to extract a core. Other turf aeration apparatus use a V-shaped, U-shaped or X-shaped stake as the tine, although these devices may or may not extract a core. Solid tines may also be used in place of hollow tines. Other turf aeration apparatus use a barrel arrangement with the tines positioned around the barrel such that cores are created as the barrel is rolled over the grass turf. Still other turf aeration apparatus may use a drilling arrangement in which a bit is rotatably inserted into the grass turf and then withdrawn to produce a core; however, this arrangement is not preferred for treating larger areas of grass turf due to the lengthy time required to extract each core and the inability to easily create simultaneous cores using multiple tines.
Because of the continual wear that results from repeated insertion of the tines into the turf, it is necessary to frequently replace the tines. The shape of the tine is typically tapered and the surface of conventional tines is smooth so as to minimize the friction that results from repeated insertion of the tines into the turf. Many of the improvements in turf aeration apparatus have focused on the manner in which the tines are connected to the turf aeration apparatus so as to allow for more convenient replacement of the tines. Examples of these arrangements can be found in U.S. Pat. Nos. 4,574,890, 4,638,867, 4,785,889, 4,881,602 and 5,495,895.
Some improvements to the tines themselves also have been made. U.S Pat. No. 3,586,109 describes a hard wear-resistant ring element that fixed to the lower end of the tine and forms the portion of the tine that affects the cutting of said turf to improve durability. U.S. Pat. Nos. 3,797,577 and 4,924,944 describes tines having openings in a side of the tine for ejecting the core in a different manner than out the top or bottom of the tine.
While core cultivation is essential for maintaining turf quality, it does little to actually alleviate compaction. Removing a core of compacted soil and replacing it with sand will certainly reduce compaction, but this reduction in compaction only occurs in that hole. It has been found that when a tine is inserted into the ground, the force it takes to insert the tine causes pressure to be applied outward. (Petrovic 1979). Rather than reducing compaction around the core hole, the tine itself increases compaction to the base of the core and along the core wall. xe2x80x9cThe results to date are conflicting in that core cultivation has improved or had no effect on alleviating compaction and in several cases created more compaction (Waddington, et. al., 1992). It is also the case that any improvements in infiltration capacity due to core cultivation may last only a few weeks or a month. (Byrne, et. al., 1965).
Although core cultivation may not directly improve compaction, there has been a generally accepted belief that core cultivation serves a long-term benefit. xe2x80x9cIf holes are punched regularly on a monthly basis, compaction can be relieved in 6-10 years.xe2x80x9d (Madison 1971). Fortunately, there are also short-term benefits that make core cultivation worthwhile, such as stimulated root activity, release of toxic gases, and disruption of soil layers. When coupled with the short term improvements in infiltration capacity provided by core cultivation which also last about a month, it has become accepted practice in the turf management industry to recommend the use turf aeration apparatus to perform core cultivation on a monthly basis for high traffic areas such as golf greens and athletic fields.
Even though existing turf aeration apparatus are useful in enhancing the viability of turf grass in compacted areas, it would be desirable to develop an apparatus for core cultivation that not only decreased compaction in the aerified hole, but also decreased compaction around the hole. It would be advantageous if the use of this apparatus for core cultivation also retained infiltration effectiveness over a longer period of time without reducing the benefits of the conventional coring method. Most of all, in order to please the ever escalating demands of golfers and turf managers alike, the disturbance of the turf must be minimal after the application of such a new core cultivation technique.
The present invention is an abrading tine for use with a turf aeration apparatus. Preferably, the tine is a coring tine comprised of a hollow metal tube having a proximal end and a distal end. Abrading structure is defined on and protrudes from an outer surface of the tube such that the abrading structure forms at least ten discrete protrusions per tine and such that a distance between a peak of each protrusion and the outer surface ranges from greater than 1 mm to less than 12 mm. The abrading structure is defined such that a significant increase in water infiltration and root mass of the grass turf is achieved as compared to a conventional smooth tine. The abrading tine is adapted to allow the proximal end of the tube to be operably coupled to a vertically poweredturf aeration apparatus by any number of known attachment arrangement. The tube may be slightly tapered and the distal end beveled for easier insertion into grass turf. The abrading structure can comprise a plurality of grating elements or a knurled pattern defined in the outer surface. In one embodiment, a metal sheet having grating elements comprised of apertures and corresponding raised structures is welded around the tube. In another embodiment, a knurled or threaded pattern is formed on the outer surface of the tube to create the abrading structure.
Tests have confirmed that the abrading tine in accordance with the present invention will not only decrease soil compaction in the core hole, but also decrease compaction around the core hole. This improves water infiltration effectiveness for a longer period of time, and subsequently, increases root development without affecting the other benefits of the conventional turf aeration apparatus. Advantageously, the preferred embodiment of the present invention is able to lengthen typical water infiltration rates such that the frequency of turf aeration can be reduced by up to fifty percent. Similarly, root mass of grass turf treated in accordance with the present invention can also be increased by up to fifty percent.